Proportional calipers.



No. 835,466. PATENTED NOV. 6, 1906. J. PRARIO.

PROPORTIONAL GALIPERS. urmonmi-runn inn 21. mos.

I l V WITNESSES INVENTOH W I I 75/272 Hezrz'a giaww I A rro/fNEl s UNITED STATES PATENT OFFICE.

JOHN PRARIO, OF MOUNT HOPE, WEST VIRGINIA.

PROPORTIONAL cAuPERs.

Specification of Letters Patent.

Patented Nov. 6, 1906.

Application filed Tune 27, 1906. Serial No. 323,718.

liability of this relationship being accidentally varied or changed during the use of the instrument on any one particular piece of work.

In most of the proportional calipers now in use theproportion is varied by shifting the pivot-pin along slots provided in the pivoted members. In such instruments if the pivotpin or binding-screw becomes loosened or if the instrument is drop ed or jarred the cen ter may be very slight y shifted without its being noticed by the person using the instrument at the time,-and such slight shifting of the center and the-consequent changing of the proportion resulting therefrom may cause very-serious damage before the change is nobetween the points of the calipers.

ticed.

In my improved calipers I provide a series of removable legs pf ditl'erent lengths adapted to be used in connection with a single pair of pivot-ed members. The lengths of each of the pairs of removable legs when secured in place bear a sim le relation to the lengths of the non-removable legs, whereby any definite proportion may be secured by using legs of the lo-sired length.

My invention is especially adapted for use 'by sculptors and modelers who have occasion to reproduce in marble, granite, or clay and at a different scale from the original.

Several pieces of work may be in. progress at the same time and each being made to a different scale, so that it is necessary to frequently change the proportional distance By the use of my improved instrument all the difiiculty in this respect is obviated, as the removable legs may be replaced by of hers of a diiierent length whenever it is desired. to use the instrument on another piece of work.

To more fully explain my invention, reference is to be had to the accompanying drawings, which form part of this specification, in

which drawings liken'haracters of reference indicate corresponding'p'artsthroughout the views, and in which' Figure 1 is a side elevation of my improved instrument, showing in dotted lines a second pair of removable legs of different lengths than those shown in solid lines. Fig. 2 is a side elevation of the instrumentfas seen in the plane thereof, and Figs. 3 and show details of the pivoting means.

My improved calipers comprise two members 1 and 2, pivotally connected together. The member 1 is provided with a circular plate 3 and arms 4 and 5, extending from opposite points on the periphery of the late and in the plane thereof, while the mein er 2 comprises two parallel circular lates 6 and 7, spaced apart and both secure to the arms 8 and 9, extending from o posite peripheral.

points on said plates. T e plate 3 of the member 1 is inserted between the plates- 6 and 7 of the member 2, and the parts are secured together by a pivot-pin or bolt 10, having an, enlarged head 11 and a thumb-nut 12 The arms 5 and 8 are of equal length and similar shape, the two being curved to- Ward each other and each provided with a sharp point The arms 4 and 9 are preferabl straight, and each is provided with a soc et 13 and a set-screw '14, whereby the removable legs 15 and 16 may be secured thereto. The legs 15 and 16, as shown,'have their outer points at exactly four times the distance from the center of the pivot-pin as isthe distance of the points of the arms 5 and 8 from said pivot-pin. There is also shown in dotted lines removable legs 15 and 16, the points of which are three times the distance from the center of the pivot as are the points of the arms 5 and 8. It is evident that a large number of airs of these legs may be provided, the lengtli of each pair bearing a simple and definite relationship to the length'of the arms 5 and 8, and when it is de sired to use the instrument on any particular piece of work being made at a diilerent scale from the piece of Work upon which the instrument was last used the removable legs may be very quickly; and readily taken ofi" and another pair having the proper length substituted therefor.

I have shown the leg 15 as being provided with a removable marker 17, although it is evident that the leg 15 may be provided with a pointed end, as is the leg 16.

Having thusdescribed my invention, I

claim as new and desire to secure by Letters Patent 1. A pair of proportional calipers, comprising two members, each having. two legs extending in opposite directions and means intermediate the two legs and stationary as regards the ends of said legs for pivotally connecting the members together, and a piurality of pairs of detachable legs of difierent length, each pairbeingadapted to besecured directly to one end ofsaidmembers, whereby calipers havingdifferent proportional distances between opposite ends-may be formed.

2.- ,A pair Of? proportional calipers, comprising two members, one having a circular plate andtwolegs extendin from. opposite edges thereof, and the othera ving two parallel circular plates and twolegs extending from opposite edges spacingand unitingsaid plates, a pivot passing through the center of all-of these plates to hold the first mentioned plate between the two last-mentioned ones, the ad'acent legsof the two members on one side 0 the center being curved toward each other. and the adjacent legs of. the other ingstraight and extending to substantially the same distance from the cent-er as the opposite curved legs, the ends of each of'said straight legs being provided with a socket and set-screw, and a, plurality of detachable legs of difierent lengths, each pair being a apted tobesec'uredin said'sockets whereby calipers havingidiflerent lengthsmay'be formed; 7

In testimony whereof I- have signed my name to this specification in-the presence of two subscribing witnesses.

Jenn PRARIO;

- Witnesses:

I Gno. M n-Lian, S. T. Barrier.

members on the other side of the center he- 

